Can Domestic Selection cause Macroevolution?

Just a point of correction: a number of parasites induce behavioral or other changes in their hosts - especially intermediate hosts. One example:Robb T, Reid ML, 1996 “Parasite-induced changes in the behaviour of cestode-infected beetles: Adaptation or simple pathology?”, Canadian Journal of Zoology/Revue Canadien de Zoologie. Vol. 74, no. 7, pp. 1268-1274.

quote:

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Abstract:

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Although the cause is often unclear, many parasites alter the behaviour of their intermediate hosts. The larval form of the rat tapeworm, Hymenolepis diminuta, has previously been shown to modify the behaviour of its intermediate host, the flour beetle, Tribolium confusum, in a manner that may be adaptive to the parasite. To test this explanation we observed host behaviours including activity, concealment, and the response to and production of pheromones. Infected female beetles examined both 4-5 and 11-12 days post infection were slower moving and slower to conceal themselves than uninfected conspecifics; however, they did not differ from uninfected individuals in staying concealed. Infection of T. confusum did not affect the production of pheromones by mated and virgin females or the response of females to male pheromones. A second hypothesis for altered behaviours may be that modified behaviours result from pathology. The survivorship of mated infected female beetles was significantly lower than that of infected virgin beetles and uninfected beetles. Thus, both mated status and infection were important factors in survivorship, but only infection had significant effects on the altered behaviours. In this system, therefore, the hypothesis that behavioural changes are due to adaptive manipulation of the host by the parasite is supported.

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I think this is a pretty clear indicator that at least sometimes parasites DO alter their hosts for their own benefit.

Hi there, O Tusked Hairy Extinct One! I wish I could be around a lot more, but I have little time to do much more than lurk occasionally. How's the book going?

Hi EZ,As an ecologist (but not a biologist although I play one on TV ), I also tend to separate parasitism from the other types of symbiosis when talking to other ecologists. However, the fact remains that in almost all textbooks (at least at the undergrad level) with which I'm vaguely familiar, parasitism is included under symbiosis. I think its reasonable to do so. Consider: it's often very difficult to tell whether a relationship is mutualistic or comensal - or parasitic. Think of the Acacia/Pseudomyrmex complex. Not all Acacia acacia have a mutualistic relationship with the ants. Indeed, some Pseudomyrmex species actually "take advantage" of Acacia's pro-ant adaptations without providing any reciprocal benefit. Hence the latter could be considered "parasitic" on the tree, even tho' most Pseudomyrmex species ARE obligate mutualists with them.One of the reasons I love field ecology is that things are often really complicated, and simple generalizations don't always work.ABE: Also look at the Cecropia/Azteca complex. Another example where how you define ant-plant symbiosis is dependent on the particular species - some Azteca are obligate mutualists, some are more on the lines of comensalists or even "parasites" if you figure in the energy expenditures of the tree used to provide the ants with everything from internodes for nesting sites to trichilia and mullerian bodies for food while the ants don't defend the tree at all. Just take advantage of the goodies the tree produces. Parasite, mutualist or do we need a new term?This message has been edited by Quetzal, 04-07-2006 09:22 AM

I was kidding. Most of the places I work don't even have electricity, let alone TV. I am now totally in love with that word. Did you just invent it or is it in common usage? I have a "cleptoparasite" living in my back yard - the glossy flowerpiercer (Diglossa lafresnayii) that bypasses the pollen and punches a hole in the bottom of the flower's nectary. Pretty bird, tho'.

Thanks for the article. I've downloaded it into my "neat to keep" files.Guatemala, nope. Formerly Nicaragua, now Ecuador (they still have quetzals, but they're pretty pitiful compared to the Nica or Guatemalan subspecies).